In recent years, the rising cost of fuel has sharply increased the need for more efficient consumption of fuel. One well known, but little used method of efficient fuel consumption in a motor vehicle lies in the conscientious use of fuel saving driving techniques. In fact, a 1978 United States government publication entitled "Driver Aid and Education Test Project" (DOE/CS-0043) and prepared for the U.S. Department of Energy states, on page 1, that it is ". . . not unusual to find a variation of 30 to 50 percent in fuel economy among a group of non-professional drivers operating under identical and controlled test conditions . . . ", the difference being attributable solely to individual driving techniques. Thus, it is clear that significant amounts of fuel could be saved by the widespread adoption of fuel efficient driving techniques by the motor vehicle operators of this country.
To encourage the use of such efficient driving techniques, a variety of fuel consumption gauges and indicators have been provided by the prior art. Such prior art fuel consumption gauges have typically utilized a vacuum operated sensor to monitor the manifold pressure of the engine, as the manifold pressure is one of the best over all indicators of efficient fuel use. A high vacuum pressure in the engine manifold indicates that the fuel is being burned in a fuel to air ratio which results in complete, and hence efficient, combustion. By contrast, a low vacuum pressure in the manifold indicates that the fuel is being burned in an overly rich fuel to air ratio which results in incomplete, and hence inefficient, combustion. In operation, the vacuum operated sensor of typical prior art devices senses whether the pressure of the engine manifold is in a high or low vacuum state, and transmits this information to an indicator which in turn indicates to the driver whether or not the motor vehicle is being driven in a fuel efficient fashion.
Unfortunately, each of the prior art fuel consumption indicators has, thus far, been attended by a variety of technical drawbacks which in turn has discouraged its general use among the motor vehicle operators of this country. For example, Polymeros U.S. Pat. No. 2,666,197 discloses a vacuum operated signal device having a vacuum operated switch adapted to be mounted on the instrument panel of an automobile. However, the single pilot light of Polymeros' invention only gives a visual indication of an inefficient fuel consumption condition in the engine which is easily overlooked by a driver observing the road. Further, the suggested location of the single pilot light of this invention between other lights and indicators on the instrument panel of the automobile makes installation difficult, and renders the single pilot light less perceptible to the driver than if the signal light were mounted away from the other lights and dials of the instrument panel. Finally, because the pilot light is actuated only during a fuel wastage condition in the engine, it is difficult to tell at any given time whether or not the invention is operative.
While Corsseu U.S. Pat. No. 2,683,782, Shuck U.S. Pat. No. 2,870,753, and Platt U.S. Pat. No. 2,692,980 each disclose manifold pressure indicators utilizing two separate signalling devices for signalling both efficient and inefficient fuel consumption conditions in an internal combustion engine, they suffer from the drawback of utilizing relatively intricate and expensive single pole, double throw or double pole vacuum operated switches. Additionally, each of these devices utilizes only a pilot light for indicating an inefficient fuel consumption condition which again can be easily overlooked by an operator with his full attention on the road.
Finally, although the manifold pressure indicator disclosed in Australian Pat. No. 114,535 suggests the use of an audio signal to signal an inefficient fuel condition, this device, like the Polymeros invention, is capable of signalling only an inefficient fuel consumption condition. Additionally, no suggestion is made as to how to conveniently mount this device in the cockpit of a conventional motor vehicle.
Clearly the need exists for a conveniently installable, simple, effective and inexpensive fuel consumption signalling system which has at least two separate signalling devices for positively signalling both efficient and inefficient fuel consumption conditions.